Switching is a mechanism to connect different networks or different components of a network. Circuit switching and packet switching are two different kinds of switching. For data transfer through circuit switching, a dedicated path is employed between the source and the destination. However, packet switching is a connectionless technique. Initially, the circuit switching technique was designed for voice communication and the packet switching technique was designed for data transfer. Generally, the packet switching method is far more efficient than the circuit switching method. These two techniques have interesting differences, which will be discussed below.
Circuit switching is a method of switching, which uses a dedicated connection between the sender and the receiver for data transfer. There are three phases of circuit switching, which are as follows,
Circuit Establishment: A dedicated physical route is established between the sender and the receiver. The path may include a number of intermediate switching centers.
Transfer of Data: After the establishment or setup phase, data is transferred through the dedicated path.
Circuit Disconnect: Once the data transfer is done, the circuit is disconnected from one of the ends. All the intermediate links are disconnected in this phase.
Circuit switching is usually used in telephones. The routing between two telephones is shown below,
In the packet switching method, the data is broken into “pieces” or “packets” and transmitted individually from the source to the destination. Upon receiving, the packets are reassembled at the destination. This method does not require any pre-established dedicated route. The types of packet switching are,
Virtual Circuit Based Packet Switching: In this mode of packet switching, virtual circuits are established for each packet. Each packet is transmitted through the predestined route. This mode has similar phases as the circuit switching method.
Datagram Based Packet Switching: In this mode, every packet has two parts, which are a header and a payload. The header of a packet contains the required information (e.g. source and destination addresses, port identity, etc.). The payload contains the original data. The packets are transmitted randomly without any predestined path. At the receiver end, all the packets are arranged and assembled, based on the header information.
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The comparison between circuit switching and packet switching is shown in the following table,
A dedicated connection is required.
Data is transferred in three phases. At first, a dedicated route is established between the source and the destination. Then, the data is transmitted and after that, the circuit is disconnected.
The data is broken into packets of variable lengths, each of them containing a header (carries addresses) and a payload (carries actual data). The packets are transmitted randomly and assembled at the destination.
The circuit route is inflexible.
The routes for the packets are flexible.
The data is processed at the source end.
The data is processed at nodes and the source.
Usually used for voice communication.
Used for data communication.
Time-division switching and space division switching.
Virtual circuit switching and datagram switching.
Implemented at physical layers.
Implemented at network works.
Effective for continuous and long transmission. The dedicated path ensures steady communication.
Delay in communication is less. Due to the flexible routes, the method is almost immune to network failures. This method has better bandwidth coverage.
The inflexible route cannot be used for multiple data transmission. Bandwidth requirement is very high.
High installation charge and complex structure.
Apart from circuit switching and packet switching, there is a third type of switching namely message switching. This is a connectionless technique, where an entire message is routed from the source to the destination, through a number of intermediate nodes. Each node stores the data and then forwards it to the next node.
Packet switching is derived from the message switching technique.
The concept of packet switching was invented by Paul Baran.
Circuit switching is effective for voice transmission and packet switching is effective for data transmission.
1.What is circuit switching and packet switching? What are the differences?
Circuit switching is a switching method that uses dedicated physical routes between the sender and the receiver. The process is carried out in three phases. At first, the physical route is established, followed by the data transmission. At last, the path is disconnected from any of the ends. Circuit switching is generally used for voice transmission.
Packet switching is a connectionless switching technique. The data is broken into packets or units, which are transmitted to the destination via individual routes. The routes are flexible. Each packet consists of two parts: header and payload. The header carries the information regarding the source and destination addresses whereas the payload carries the original data. Packet switching is effectively used in data communication.
2. Write down the difference between message switching and packet switching.
In the message switching method, only one datagram (message) is transmitted to the destination. The message hops through intermediate stations. Each station stores and then forwards the data. In the packet switching technique, multiple packets of data are generated. The packets are sent to the destination via flexible routes, depending on their header information.
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